Radio telephones, in particular battery powered hand portable telephones, have been designed to be smaller and more lightweight than ever before. This is due to user requirements for small, lightweight mobile terminals. However, users also require longer periods of use of the mobile terminals before the battery requires replacing or recharging. This requirement is in conflict with the requirement that mobile terminals are small and lightweight, since a battery's current capacity is proportional to its weight and/or volume. Thus, in order to increase the time period of operation of a mobile terminal between recharging or replacing of a battery, effort has been made to reduce the power consumption of the mobile terminal, as well as attempting to increase the power to weight (volume) ratio of the batteries for the mobile terminal.
For a mobile terminal there are two distinct modes of operation, each characterized by different power consumption levels. In the first mode, known as an "in call" mode, power consumption is high since the mobile will be periodically transmitting up to 0.8 watts of power for a Class III PDC hand portable for example. The second mode is the "standby" mode. In this mode the mobile terminal operates on a low current consumption for internal housekeeping of the mobile terminal such as a clock, only periodically "waking up" to receive information signals such as paging information from a base station of the radio telephone network. Even when receiving signals the power consumption of the mobile terminal is much lower than when it is transmitting.
Typically, a user of a mobile telephone does not make many calls, and if they do they accept high power consumption. However, users are concerned with the length of standby time, and this is an important marketing feature of a mobile terminal.
FIG. 6 shows a typical radio telephone. The portable radio telephone shown in FIG. 6 is a cellular telephone 1 powered by a rechargeable battery pack. The telephone 1 includes a transceiver 8 comprising a receiver and transmitter and all the other features 9 conventionally found in a cellular telephone. Also, since these aspects of the telephone are not directly relevant to the instant invention no further details will be given here, except to say that a single microprocessor 4 is employed to control all the basic functions of the telephone 1 and to control the keypad and display functions.
Optionally, however, the telephone functions may be controlled by a master microcomputer, while the keypad and display functions are under the control of a separate slave microcomputer coupled to communicate with the master microcomputer.
The user-interface of telephone 1 comprises a display, e.g. a liquid crystal display 5, itself well-known in the art and a keypad 6 on the front of the telephone 1. The display is coupled to and regulated by the microprocessor 4 in the usual manner. The keypad 6 essentially comprises two main sets of keys, namely alpha numeric keys 6a associated with alpha numeric data especially for dialling telephone numbers, but also (optionally) for entering alphanumeric data into the telephone memories, e.g. a subscriber number index, and a set of function keys 6b for enabling various predetermined functions or operations.
The keys 6a are arranged in four rows of three keys each. As is conventional for the numeric key layout of a telephone, the top row comprises keys for numbers 1, 2 and 3 respectively, the second row down for numbers 4, 5 and 6 respectively, the next row down for numbers 7, 8 and 9 respectively, and the bottom row for *, 0 and # respectively. Some or all of these keys may also be associated with alphabet information, as again is quite conventional. The alphabetic rather than numeric data is selected for example by preceding the alphanumeric keystroke with another predetermined keystroke or set of keystrokes, specifically using the function keys. Hence the alphabetic data mode may be enabled for example by preceding the particular keystroke with previously depressing a "MEMORY" or "STORE" key disposed among the function keys 6b.
As is usual in cellular telephones, the keys 6b include a "SEND" and "END" key for respectively initiating and terminating a telephone call. Another key, specifically located in the top left-hand corner is an "ON/OFF" key for turning the telephone on and off, i.e. by connecting and disconnecting the battery pack power supply. Another of the function keys may be a menu or function key labelled, for example, "MENU" or "FUNCTION" or with a suitable abbreviation thereof. Depression of this key enables a variety of pre-set menus, the related instructions of which are stored in memory, to be viewed and selectively enabled. The various menus are selected by depressing the appropriate alphanumeric keys after depressing the "MENU" or "FUNCTION" key. The relevant menu is shown to the user in words or abbreviations on the display panel 5.